1. Field of the Invention
The present invention relates to a plasma etching method.
2. Description of the Related Art
In a plasma etching apparatus, for example, a parallel plane-typed plasma etching apparatus, RF power is applied to an upper electrode, a lower electrode supporting a wafer is grounded. An etching gas is introduced between both electrodes and plasma is induced, thereby performing an etching process of the wafer.
For example, as shown in FIG. 2, in a case where an oxide film (SiO.sub.2) 52, which is an etching material, formed on a Si substrate 50 is etched, the etching has been performed in such a manner that the portions except the etching portion are masked by a masking member 54 and etching gas is introduced therein.
In this case, there was necessity for a selection ratio defined below to be improved. ##EQU1##
In order to improve the etching grade of SiO.sub.2, such improvement was conventionally made by the selection of etching gas.
As mentioned above, since the element, which determines the etching characteristics, conventionally depended on the selection of etching gas, there was a problem in that if the selection of etching gas was changed, this had a great influence on the other etching characteristics.